the GiGLer

The newsletter of Greenspace Information of Greater London CIC

Street Trees

Matt Davies, GiGL Data Manager

In the winter of 2008, we discussed how GiGL had been commissioned by the Capital Woodlands Project to help identify areas of London lacking street trees.

In this article, we return to the subject but take a broader look at street trees in London and at aspects of street tree data management.

The London Assembly’s 2007 report, Chainsaw Massacre, highlighted ‘the unfortunate practice of removing broadleaf trees to avoid subsidence damage claims’. At the same time, they found that ‘Londoners value the shade and cooling that urban street trees offer in the summer, how they improve street environments and reduce noise and dust from road traffic [and] crucially, how they also mop up carbon emissions’.

This report led to the creation of the Mayor’s street trees programme, which aimed to plant 10,000 additional street trees by March 2012 across 40 priority areas – those with the fewest street trees that would most benefit from the social, economic and environmental improvements that trees provide. It has been a major success. Applications for the fourth and final round of the programme have now closed and the final 500 trees will be planted this winter.

It is especially satisfying that the priority areas were identified using a GIS model that GiGL created.

In creating the model, GiGL collated data from the London boroughs on street tree location, height, girth, canopy and age, and other attributes. Recognising the potential of this London-wide dataset for other projects, GiGL worked with The Forestry Commission and the London Tree Officers Association to create a bespoke data exchange agreement. This allows two-way exchange of tree data between GiGL and its partners but, at the request of the tree officers association, does not provide the data to the National Biodiversity Network or to commercial customers.

Currently around a third of boroughs have agreed to participate in this exchange of tree data and we hope more will join as the benefits become clear. The usefulness of a London-wide tree data set is also apparent to the GLA, and to the London Assembly who state, in their recent report Branching Out, ‘There is a ready and robust dataset available through GiGL, but it would require boroughs to agree to submit their data on an annual basis. We do not think this would present a disproportionate bureaucratic burden or be expensive. … it would allow a records management organisation (such as GiGL) to manage the data on boroughs’ behalf, thereby alleviating tree departments of that cost’.

With GiGL managing a London-wide tree dataset, we could carry out useful statistical analyses, using tree data alongside other GiGL datasets, under existing borough service level agreements. For example, we could:

•    Work out trees at risk of disease using records from the London Invasive Species Initiative.

•    Estimate the proportion of different tree species to the overall canopy.

•    Based on surrounding species and habitats, to inform planting of the right tree in the right place.

•    Ensure tree records contribute to other agendas, such as:

  • Nature improvement areas
  • London Biodiversity Partnership habitat suitability model
  • London Wildlife Trusts garden campaign
  • All London Green Grid

We have also been approached by the London Tree Officers Association about the possibility of putting their tree data on the soon to be launched iGiGL mapping interface. If funded, this project could enable members of the public to find trees of interest and request specific services such as pruning and disease treatment, and specify how urgent the request is. It could also aid borough tree officers responding to such requests, and allow the general public to add new tree records where these appear to be missing from the borough data, for instance where a tree is in private garden.

All things considered, we have come a long way since the Chainsaw Massacre report, and we hope to build on successes to date so that the GiGL partnership can soon realise the full benefits of a London wide tree dataset.

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